Hydraulic draft gear



Sept. 6, 1932- J. A. MCGREW 1,375,145

HYDRAULIC DRAFT GEAR Filed Aug. 14, 1929 2{ are a a /5 Sr' /i 4 ff Patented Sept. 6, 1932 UNITED STATES JOHN A. HCGBEW, or ALBANY, NEW YORK nmaomc mmrr em Application filed August 14, 1929. Serial Ito/385,817.

This invention relates to improvements in shock absorbing mechanisms and particularly to the type which is adapted to absorb and dissipate the energy of shocks incident to '8' the movement of heavy bodies, for example, railway draft gears, bufi'ers or the like, or which may be adapted to cushion the moving parts of machinery.

It is an object of this invention to provide a hydraulic shock absorbin device of this type which is particularly a apted for use in connection with a railway draft gear by reason of its ability to dissipate and absorb the shocks incident to the starting or stopping of the modern heavy rolling stock, within the small limit of travel of the moving parts of the draft gear which is permitted under standard practice.

Other objects and features of novelty will be apparent from the following descrlption when read in connection with the accompanying drawing in which one embodiment of the invention is illustrated by way of example:

Figure 1 is a plan view of the draft gear embodying the principles of the invention, together with its connections to the underside of a car;

Figure 2 is a vertical, longitudinal, cross sectional View of the shock absorber unit taken on line 22 of Figure 1;

Figure 3 is a horizontal, longitudinal, cross-sectional view of the same element; and

Figure 4 is a vertical, transverse, cross-sectional view taken on line 4-4 of Figure 1.

Referring to Figure 1 of the drawing, the numeral 10 denotes generally the novel shock absorber unit which is dis osed within the yoke 11 and between the ront follower 12 and the rear follower 13. The front follower 12 is adapted to abut the front stop lugs 14 and the rear follower 13 similarly abuts the rear stop lugs 15. These front and rear stop lugs 14 and 15 are attached in the well known manner to the inner sides of the draft sills 16 which are disposed centrally of the underside of the car body. The yoke 11 is provided with the forwardly opening jaws 17 which are provided with lateral perforations 18 which are adapted to register with the opening 19 in the rear end of the draw bar 20.

A coupler key 21 passes through these registermg openings 18 and 19 and also through the elongated slots 22 provided in the draft 51115. All of these elements are conventional parts of the draft gears now in use except 65 the compression element or unit 10 which forms the subject matter of the present invent on, and it will be noted that this element 10 disposed between the followers 12 and 13 is adapted to replace the conventional springs, wedges and other devices which are now in general use.

The compression unit 10 comprises but three prlnclpal parts, the outer casing part 23, the inner casing part 24, and the coil spring 25. The inner part 24 of the casing is adapted to telescope within the part 23 with a fluid tight sliding fit between the cylindrical outer wall 26 of the inner part and the inner wall 27 of the outer part. This outer member 23 is rectangular in cross-section and is provided with an end wall 28 at the end of said member opposite to the end into which the inner member is introduced- This end wall 28 is centrally provided with an inwardly directed circular protuberance 29. The central portion of this protuberance 29 is drilled out as at 30 to provide a pressure chamber which is enclosed by the annular walls 31.

At the opposite end of the outer member 23 two oppositely disposed chambers 32 are provided between the inner walls 27 and the outer walls 33. These chambers 32 form a part of the fluid reservoir which is provided in the outer casing and which includes also the chamber 34 which lies between the annular wall 31 of the pressure chamber 30 and the outer wall 33 of the outer casing member 23.

The inner casing member 24 is provided with an end wall 35 which is centrally provided with an inwardly projecting cylindrical piston member 36 which is adapted to enter the pressure chamber 30 and is formed with a slightly less diameter than that of the chamber 30 so as to provide a slight clearance between the walls of the piston mem her and the walls of the chamber 30 as at 37. Between the cylindrical outer walls 26 of the inner member 24 and the piston member 36 lies an annular chamber 38 in which there is disposed the coil spring 25. One end of the coil spring abuts the inner face of the end wall 35 of the inner member 24, and the other end of the coil sprin abuts the end portions 39 of the annular wall 31 which-forms a part 0% the protuberance 29 on the outer member 2 It will be seen from Figure 4 that the inner wall 27 and the outer wall 33 of the member 23 merge as at 40 on the opposite sides of the member 23. Openings 41, into which the plugs 42 are threaded, are provided in these oppositely disposed wall portions 40 and are adapted to project inwardly within the grooves 43 as clearly shown in Figure 2 of the drawing. The length of the grooves 43 is predetermined in accordance with the desired or permitted distance of travel of the draft gear, which under standard practice is about 2% inches. It will be seen that, as well as providing a stop means for either direction of travel of the parts 23 and 24 relatively to each other, these plugs and slots 42 and 43 also provide means for preventing rotation between the inner and outer casing members, and consequent possible distortion of the spring 25.

Upon one of the shorter outer sides of the outer casing member 23'there are provided the filling openin s 44 through which a suitable fluid, prefera ly oil, may be introduced to the casing, and which may be stopped by any suitable means such as plugs 45.

In operation, whenever a sudden draft force is applied to the draw bar 20, the yoke 11 will cause a sudden forward movement of the rear follower 13 and consequently the outer casin member 24 of the compression unit 10 will e forced into the outer member 23. This movement will also cause the piston member 36 to enter the pressure chamber 30 and force the fluid which occupies this chamber 30 through the narrow annular passageway 37 into the piston chamber 38, which together with chamber 32 and 34 form a reservoir for the fluid. The size of the annular by-pass passageway 37 is selected so that considerable resistance is offered to the passage of fluid therethrough. This resistance toether with the compression of the spring 26 etween the end wall 35 and the abutment face 39 of the annular wall 31 offers considerable resistance to the compression of the unit 10 and effectively dissipates and absorbs the shocks attendant upon starting the rolling stock. Upon receipt of a buffing shock, the draw bar 20 will be forced rearwardly against the forward follower 12, and thus the outer casing member 23 will be moved rearwardly with reference to the inner casing member 24 and the same relative movement and shock resisting compression will take place. Upon cessation of the draft or bufiing movement, the spring 25 will cause the memhere 23 and 24 to'resume their extended positions, and some of the fluid from the reservoir will return through the passageway 37 and refill the pressure chamber 30.

It will be understood that the casin is only partly filled with oil or other suitabfii liquid so as to provide space for that part of the fluid which is displaced by the piston 36 and other portions of the inner member 24 upon compression or the unit. Since the leakage of fluid from the compression unit between the walls 26 and 2? is negligible, the casing need be refilled with fluid only at infrequent intervals. There thus provided an exceedingly strong, simply constructed shock absorbing body formed with a minimum number of parts which is not likely to get out of order and which may be readily substituted for present shock absorbing devices used in connection with standard draft gears. This invention also provides a hydraulic draft gear which is adapted to sustain the heaviest shocks to which it may be subjected and to dissipate and absorb them during relative movement between its component parts. the distance of said movement not exceeding that permitted under standard practice. It will be readily apparent to those skilled in the art that the design and arrangement of the com onent elements of the invention may be considerably modified without departing from the spirit and scope of the invention as set forth in the appended claims.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. In a hydraulic draft gear for a railroad car, a compression member adapted to be disposed within the yoke and betweenthe front and rear followers of said draft gear, said compression member comprising a two part casing adapted to contain a suitable fluid, one of said parts being adapted to telescope within the other of said parts, said first named part being provided with a cylindrical side wall and an outer end wall, said outer end wall being provided with an inwardly projecting cylindrical piston member, said side wall and said piston member enclosing between them an annular cylindrical spring chamber, the second named part being rectangular in cross section and provided with end walls, one of said end walls being provided with an opening into which said first named part is adapted to fit, the other of said end walls being provided with an inwardly directed annular protuberance within which is formed a pressure chamber of slightly greater diameter than said piston member and into which said piston member is adapted to enter upon compression of said element, whereby said fluid is caused to pass between said piston and the walls of said pressure chamber, a fluid reservoir surrounding said protuberance and extending toward the other end of said parts on two opposite sides of said first named part, cylindrical guide walls adapted to enclose the outer walls of said first named member with a fluid tight sliding fit and forming inner walls for portions of said reservoir, a coil spring disposed within said springchamber and adapted to be compressed between the end wall of said first named member and the inner end of said annular protuberance, the inner end of the cylindrical side wall of said first named member being adapted to vary the opening be-v tween the reservoir and said spring and pressure chambers.

2. In a hydraulic draft gear, a compression member comprising a two part casing .adapted to contain a suitable fluid, one-of said parts being provided with a pressure chamber and a reservoir, the other of said parts being provided with a piston, a spring chamber and a cylindrical wall adapted to project towards said other part, said piston adapted to enter said pressure chamber, and to force fluid from said pressure chamber into said spring chamber and said reservoir, said cylindrical wall forming a variable closure between said spring chamber and said reservoir.

3. In a compression element, a two part casing adapted to contain a suitable fluid; the outer one of said parts adapted to enclose the inner one of said parts arid being provided with an outer wall and two annular inner walls spaced from said outer wall to form a fluid reservoir, one of said inner walls extending from each end of said outer part for a portion of the length thereof toward the longitudinal mid-portion of said outer part, one of said inner walls enclosing a pressure chamber, and the other comprisin a fluid-tight guideway for the inner part 0 said casing; said inner part comprising an imperforate plunger adapted to enter the pressure chamber of said'outer part with such clearance as to provide an-annular pas-- sageway which constitutes the sole means for by-passing fluid around said piston, whereby said fluid is adapted to flow from said pressure chamber to said reservoir upon compression of said element, and a wall surrounding said plunger and spaced therefrom to proyido a spring chamber therebetween and also adapted to slidingly engage the guideway provided by one of the inner walls of the outer part; and a coil spring adapted to 00- cupy said spring chamber and to expand said element upon cessation of said compression whereby a portion of said fluid in said reser-" voir is adapted to flow back around said piston into said pressure chamber.

4. A compression member adapted for em-.

ployment in a draft gear comprising, in combination, a two part telescoping casing, a coil compression spring contained within said casing and continually tending to separate said parts, a raised annular spring abutment formed interiorly of one of the ends of the outer part of said casing, an annular spring pocket formed in the inner part of said casing, a coil spring disposed within said pocket and adapted to contact said spring abutment; and an auxiliary butting arrangement comprising a chamber having an open end formed within said spring abutment and adapted to contain an incompressible fluid, an imperforate plunger projecting from said inner part and adapted, upon compression member, to enter the open end of said chamber and force said incompressible fluid out of the open end of said chamber around the edges of said plunger.

5. A self-contained hydraulic compression element for draft gears or the like, comprising, in combination, a pair of telescoping casin members, the outer one of said members eing provided with an annular wall projecting inwardly from one end thereof, said wall being considerably shorter than said casing member and adapted to divide said member into an outer annular fluid reservoir portion and a central press e chamber, a plunger formed on said inner telescoping casing member and adapted to enter said pressure chamber with a slight clearance and displace the fluid therein upon compression of said element under a draft or bufling force, said plunger being of such length as to normally be disposed exteriorly of said pressure chamber, and means for restoring said element to normal extended po sition upon the cessation of said force.

6. In a compression element, a two part casing adapted to contain a suitable fluid; the outer one of said -parts adapted to enclose the inner one of said parts and being provided with an outer wall and two annular inner walls spaced from said outer wall to extending from each end of said outer part for a portion of the length thereof toward the longitudinal mid-portion of said outer part, one of said inner walls being relatively short enclosing a pressure chamber, and the other comprising a fluid-tight guideway for the inner part of said casing; said inner part comprising a plunger adapted to enter the pressure chamber of said outer part with a slight clearance and displace the fluid therein upon compression of said element, said plunger being of such length as to normally be disposed exteriorly of said pressure chamber, and a portion adapted to slidingly engage the guideway provided by one of the inner Walls of said outer part.

- In testimony whereof I hereunto aflix my JOHN A. MOGREVV.

' signature.

of said form a fluid reservoir, one of said inner walls 

